A DNA strand
Deoxyribonucleic acid (DNA) comprises two nitrogenous base groups, purines and pyrimidines. Purines found in the human DNA are adenine and guanine. However adenine and guanine can undergo metabolic breakdown to generate hypoxanthine and xanthine, respectively. Since purines cannot be tested for directly, their byproducts, xanthine and hypoxanthine, are generally tested for in order to detect the purine levels in your body.
Kossel's Test
There are three main tests to detect purines in humans: Kossel's test, Hoppe-Seyler test and Hugo Weidel test. Kossel's test is used to detect the presence of hypoxanthine. In this test a small amount of urine is treated with zinc and hydrochloric acid along with excess of sodium hydroxide. If the solution turns red in color, presence of hypoxanthine is confirmed.
Hoppe-Seyler Test
Hoppe-Seyler test is employed to detect xanthine. In this test, urine is concentrated and the residue is obtained for testing with the help of a strong alcohol. Then the mixture is evaporated and precipitated with lead acetate and ammonia. This precipitate is treated with boiling alcohol, and after cooling it is precipitated with ether and lime and chlorine is added to it. If the mixture turns dark green, presence of xanthine is confirmed.
Hugo Weidel Test
Hugo Weidel is also used to detect the presence of xanthine. The substance (urine) is bathed using chlorine water and nitric acid. Then, after evaporating, it is exposed to ammonia gas. If the substance turns purple or pink, xanthine is present.
Functions of Purines
There are two major cellular functions for purines in humans. First, purines along with pyrimidines (cytosyine, thymine and uracil) help in the synthesis of DNA and RNA. The nitrogenous bases of purines are linked by phosphodiester bonds and are incorporated in the growing strands of the new DNA or RNA during their synthesis. Secondly, purines also help in storing energy for the short term. The general form of energy stored by purines is ATP or adenosine triphosphate.
Ill Effects
Uric acid is produced as a result of the breakdown of purines. Generally, the uric acid is utilized for various metabolic processes within the body, while the excess is excreted via urination. However, in people whose diet is too protein rich, the levels of uric acid exceed the normal limits, thus disrupting the purine metabolism. This accumulation of uric acid around joints and tendons may result in arthritic gout.
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